Process of distilling higher fatty acids



March 3,1942. WLLS 2,274,801

PROCESS OF DISTILLING HIGHER FATTY ACIDS Filed Feb. 28, 1940 INVENTOR. Were/e Mu. L76.

BY e v ATTORNEYS,

Patented Mar. 3, 1942 rnooass or msrmnma manna FATTY ACIDS Victor Mills, Cincinnati, Ohio, assignor to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio Application February as, raw, Serial No. 321,306

10 Claims.

This invention relates to a continuous process of distilling higher fatty acids from materials containing the same. More particularly my invention relates to a process for the dry distillation of such materials, that is, distillation without the use of steam or other added gaseous medium.

The objects of my invention.are to recover such fatty acids in highly pure form substantially free from odor and light in color, to perform the distillation step continuously, to reduce operating costs, and to reduce the amount of decomposition with formation of consequent undesired by-products.

The higher fatty acids with which I am principally concerned are the saturated and unsaturated aliphatic carboxylic acids occurring in vegetable, animal or marine'fats and oils and containing from about ten to about twenty-two carbon atoms per molecule, such as oleic, linolic, stearic, palmitic, myristic, lauric, etc. The principal use of such acids is in the manufacture of soap and candles. Other impure higher fatty acids which are of less common occurrence may also be purified by distillation in accordance with my invention.

In some plants it has hitherto been the practice to distill higher fatty acids from material containing same in essentially a batch process. The fatty acid containing material, usually highly charged with coloring matter and other impurities, is fed into a still where it is heated by direct fire or other means to a temperature of about 410 to 475 F. superheated steam is introduced into the body of the material and the mixture of fatty acid vapors and steam pass out and are condensed, the whole apparatus being held under subatmospheric pressure, usually ranging from about 2 to about 5 inches of mercury absolute pressure, or occasionally slightly lower. In this operation the first portion of the fattyacids distilling over possesses a light color and is low in impurities. The coloring matter and impurities present in the crude fatty acid materialaccumulate in the still and it is usually found that because of entrainment of such matters the last portion of the distillate is much darker and less pure than the fractions distilled in the earlier stages. The impurities vary according to the nature of the raw material but consist mainly of coloring matterand unsaponifiable matter, commonly referred to as hydrocarbons, and other impurities, mostly organic in nature. Some of the hydrocarbon content is no doubt formed in the still during the distillation process due to the prolonged heating.

A semi-batch, semi-continuous process has also been heretofore practiced, in which dry molten stock is continuously fed to the batch still as fatty acid is distilled off. After a considerable amount of the impurities have accumulated in the still there is an increasing tendency for some of this material to be carried over with the distilled fatty acids, thus giving a darker colored distillate; so in order to avoid this condition some plants discontinue the distillation and/or the feeding of additional stock early enough to avoid carrying over excessive quantities of such impurities with the distilled fatty acids thereby seriously darkening the earlier fractions. In such cases the so-called still bot toms are transferred to another still wherein the last stage of distillation is carried out, the darker colored fatty acids thus obtained being redistilled to obtain light colored fatty acids if desired.

Attempts have been made to, operate a fatty acid steam distillation process continuously, in which case the raw material is fed continuously into the vacuum apparatus, the fatty acids being vaporized and continuously removed from the still and condensed,and the undistilled impurities being also continuously removed, usually with a considerable amount of undistilled fatty acids. Such processes have been disclosed in the patent to Bodman, No. 1,372,477, and to Goranflo, No, 1,951,241. My process differs from these methods and represents an improved procedure over any prior process with which I am familiar, as the following description will show.

Now one of the primary disadvantages of steam distillation lies in the formation of socalled clabber stock in the last stage of condensation. This material is an emulsion of water, fatty acid, and calcium and magnesium soaps formed by reaction of the fatty acid distillate and the calcium and magnesium salts in the water spray used for effecting the last stage of condensation. The formation of clabber stock represents a distinct loss since'the material must be given subsequent-acid treatment to recover the fatty acid which even then is of such low grade as to be undesirable for use without redistillation. The use of steam also necessitates larger electors or other vacuum producing equipment for reducing the pressure in the system and more cooling water for condensation. l

The employment of dry distillation avoids these disadvantages but introduces other disadvantages unless the steps of my process now to be described are followed.

As far as I am aware, no one up to the present time has proposed a practical process for the distillation of higher fatty ac ds in which the distillation is carried out without the aid of steam or other added gaseous medium. Such processes are commonly referred to as dry distillation processes and heretofore have not been applied commercially to fatty acid distillation because of the higher temperature necessary in dry distillation, which temperatures are known toresult in excessive charring, discoloration, and polymerization of the fatty acid material.

It has been previously pointed out that one of the requisites of dry distillation is the heating of the fatty acids to higher temperatures than normally used in steam distillation, for example, at least as high as the actual boiling point of the fatty acids under the pressure of operation. Under such conditions, operation according to prior batch or semi-batch methods is commercially impossible since excessive discoloration, charring, and polymerization are known to result from the use of such temperatures for the relatively long time necessary in such processes. Continuous dry distillation of the fatty acid must be carried out under such conditions that the fatty acid containing material is only briefly subjected to temperatures such as are necessary in the process, thereby reducing. to a minimum the harmful effects of high temperature.

In my process I accomplish this requirement by continuously and rapidly heating the crude material, without exposure to the atmosphere, to a temperature sufficiently high that the latent heat required for vaporization of the fatty acids is stored therein before the material is subjected to distilling conditions. Of course the amount of heat which may be incorporated in the fatty acid containing stock without detriment to color, etc., is limited even when the heating step is carried out continuously and rapidly. For this reason it is preferable that the absolute pressure to which the heated material is subsequently subjected be as low as possible, preferably not substantially above 0.5 inch mercury absolute, thereby reducing to a minimum the total heat required for dry, flash distillation. When the thus heated material enters the distillation chamber which is maintained under such low absolute pressure, most of the fatty acids volatilize substantially instantaneously and are removed from the heat zone before they are seriously affected by the high temperature. This step has some times referred to in other fields as flash distillation. Flash distillation is usually accompanied by the distribution of undistilled and undistillable material throughout the vapor and unless this entraimnent is satisfactorily removed from the vapor leaving the still, a dark colored distillate will result. Various well known methods of entrainment removal, such as the use of bafile plates, cyclone separators, etc., have been found unsatisfactory, primarily for the reason that in order to obtain the desired degree of entrainment removal too much resistance to the vapor flow is encountered.

, Now I have discovered a very satisfactory method for removal of entrainment comprising retaining at all times during the distillation process a small amount of undistilled or undistillable residue in liquid form in the bottom of the still proper and employing the fatty acid vapors formed on entrance of the heated fatty acid material into the still to effect continuous circulation of this residue, in accordance with the air-lift principle and/or the ejector principle, from the bottom of the still upward through a tube andagainst a batlle which is so shaped as to form a directionally controlled curtain of undistilled residue outward, downward, and away from the vapor outlet.

In my process the fatty acid vapors are continuously removed from the still, as is also the undistilled residue .over and above the small amount retained for circulation as above described. Thus by the combination of dry, low pressure distillation, flash distillation, and directionally controlled curtain of residue, I have been able to produce lighter distillates than ever before and at the same time produce still residues which are lighter in color, less polymerized, and therefore of greater value than the residues heretofore obtained.

An apparatus for use in the practice of my invention is diagrammatically shown in the dra w ing in which numeral 2 represents a sourceof heat, such as a boiler, containing a heating medium. such as a mixture of diphenyl and diphenyl oxide, which may be positively circulated by means of pump 3 through heat exchanger 4. A tank 5 serves as a source of supply for the material to be subjected to distillation and pump 6 delivers said material through pipe 1 and feed control valve 8 to the heat exchanger 4, thence through pipe 9 into the still Ill. The still I0 is provided with an undistilled residue basin ll, circulating tube [2, which is open at its ends I3 and i4, and baiile l5, the purposes of which will be more fully described hereinafter. Vapor pipe i6 conducts the vapors to condensers H and I8 which are interconnected by vapor pipe l9 and which discharge the condensed fatty acids into distillate receivers 20 and 2| respectively. Pumps 22 and 23 remove the distillate from receivers 20 and 2| continuously or intermittently as desired. The outlet of condenser I8 is connected to any of the well known types of vacuum pumps and/or ejectors. The condensers are cooled by the introduction of soft water through pipes 24 and 25 from any convenient source not shown. Any steam which may be generated in the condensers is carried off by means of pipes 26 and 21 and also through relief valves 28 and 29 if desired. The undistilled residue is continuously removed from the still Ill through pipe 30 by means of pump 33. By proper control of valves 34 and 35 or of an equivalent arrangement, the entire undistilled residue drawn off through pipe 30 may be discharged to receiver 3|, or part may be recirculated, being taken from pipe 30 by pipe 36 and introduced into the heat exchanger 4 with original fatty-acid-containing material to be heated therewith, the remainder being discharged to receiver 3| which is preferably under substantially the same pressure as the still l0 and from which the residue may be pumped by means of pump 32 continuously or intermittently as desired.

Recirculation of undistilled residue through the heater as above indicated has certain advantages which may be realized if desired. vaporization of the fatty acids in the fatty-acid-containing material requires a certain amount of latent heat which must be available at or above the fatty acid vaporization temperature corresponding to the operating pr sure. An increase in volume of material being heated without a corresponding increase in weight of fatty acid to be vaporized makes possible a reduction in temperature to which the stock must be heated in order that it may contain suflicient sensible heat to vaporize that fatty acid. Therefore by recirculating a portion of the undistilled residue and thereby diluting the incoming fatty-acid-containing material, the advantages of lower temperatures may be realized. If, however, temperature is not an item of concern and pressure is, then of course the diluted material may be heated to the same temperature that is used in operations not em ploying recirculation, thereby incorporating a larger amount of available heat for vaporization of the free fatty acids in the mixture and making possible operation at a higher pressure within the still.

The above described apparatus may be operated as follows, recirculation not being employed: The heating medium, a mixture of diphenyl and diphenyl oxide for example, is circulated by means of pump 3 or otherwise through the heat exchanger 4 and the material to be distilled containing a substantial amount of higher free fatty acid is drawn from tank 5 and pumped by means of pump 6 through pipe I and feed control valve 8 to the heat exchanger & wherein the material is heated to a sufficiently high temperature so that the necessary latent heat of vaporization of the fatty acids is contained therein.

The heated fatty acid containing material is then conducted through pipe 9 to still I0 which is maintained at an absolute pressure of about 0.5 inch of mercury or less, such as 0.05 to 0.1 inch of mercury, and wherein substantially instantaneous vaporization of most of the fatty acids takes place. As above described, the still comprises a-residue basin I l in which is substantially centrally located a circulation tube l2. The relative vertical position of this tube is so adjusted that its bottom end I3 is submerged in the undistilled residue in the still basin H and that its top or outlet end 14 is above the surface of the undistilled residue. Suitably located above the circulating tube I2 is a circular umbrella-shaped deflection baffle l5.

As will be noted from the drawing, the heated fatty acid material as introduced into the still is directed upward within the circulating tube l2.

Since the fatty acid material is heated sufficiently to effect substantially instantaneous vaporization of unvaporized fatty acids at the pressure within the still, fatty acid vapors will immediately form and by the airlift principle and/or the ejector principle will cause flow of undistilled residue and fatty acid vapors up the tube I2 and against the baflle I5. Further expansion of that portion the still. The velocity of the mixture of vapor and undistilled residue is such that as the undistilled residue strikes the bailie IS a curtain of liquid is formed, which curtain may be directionally controlled by the shape of the baflie. I have found that this curtain is very effective in removing entrainment ordinarily accompanying flash distillation probably because of the intimatecontact of the vapor with the liquid residue.

The undistilled residue continues to collect in the basin I l as distillation progresses, any excess above the predetermined amount to be kept in the basin being discharged through pipe 30 to receiver 3| which is under substantially the same pressure as the still and from which the residue is pumped continuously or intermittently as desired. The amount of undistilled residue retained inthe still basin is, of course, determined by the height of the connecting point of the pipe 30 with the basin H from the bottom thereof. The fatty acid vapors pass from the still Ill through the vapor pipe I6 into condenser H.

In order to obtain some fractional condensation of the fatty acids, I prefer to employ a series of condensers held at progressively lower temperatures. In the present illustration I have shown two condensers II and I8 together with associate distillate receivers 20 and 2! connected thereto. In the first condenser the latent heat of the fatty acid vapors is absorbed in vaporizin'g water under superatmospheric pressure, the said pressure being controlled by means of relief valve 28. The water employed in these condensers is preferably steam condensate or treated water and, as previously pointed out, is introduced into the water chamber of the condenser II, for example, through pipe 24. The steam formed bythe latent heat absorbed in condensing the fatty acids may be utilized in any way desired or may be blown off through the relief valve 28.

Vapors not condensed in condenser l'l pass through connecting pipe l9 into a second condenser l8 which is maintained at a lower temperature by allowing the heat liberated in condensation to boil steam condensate or treated water at a lower pressure than that employed in condenser I1, for example atmospheric pressure, the water entering through pipe 25 and discharging as steam through pipe 21 with or without relief valve 29 as desired. Vapors remaining uncondensed after passage through condensers II and I8 either pass into succeeding condensers maintained at progressively lower temperatures or pass through suitable equipment for maintaining the desired low pressure in the still. Since low absolute pressures are preferred in the practice of my invention, such suitable equipment comprises steam ejectors of well known type.

The condensate is collected in receivers 20 and. 2| and removed continuously or intermittently by means of pumps 22 and 23.

If it is desired to recirculate a portion of the undistilled residue and thereby obtain advantages as above pointed out, then valves 34 and 35 may be adjusted to give the desired percentage of recirculation, the temperature to which the mixture is heated in the heater 4 and/or the pressure in the still l0 being appropriately adof the fatty. acids vaporized in the heat exchanger I 4 also takes place due to the reduced pressure in justed.

It will be noted that the feed control valve is located on the inlet pipe to the heat exchanger.

Thus in the preferred practice of my invention I,

do not take the precaution to maintain suflicient pressure on the material in the heat exchanger to prevent vaporization of fatty acids therein. As a matter of fact, the fatty acid material passing through the heat exchanger in accordance with my preferred process will be subjected to a progressive reduction in pressure due to resistance to passage of the stock through the heater, for example from about twenty pounds to zero pounds gage pressure, whereby a mixture of superheated liquid and fatty acid vapors are formed before introduction into the still proper. This. 'arrangement differs over prior practice of flash distillation and has presented at least two advantages. First, the control valve is subjected to throttling relatively cool fatty acid containing material rather than hot material, thereby greatly reducing the corrosive action of the fatty acids on the valve; and, second, some of the fatty acids are permitted to volatilize on passage through the heat exchanger and thus the temperature of the material need not be carried as high as would be necessary if pressure were applied to prevent fatty acid volatilization.

Example I.-As a specific example of my pro-' ccdure employing no circulation, approximately 5000 pounds per hour of impure fatty acids resulting from hydrolysis of garbage grease are heated continuously in heat exchanger 4 to a temperature of 550-575 F. and are introduced into the lower end ii of the circulating tube II of still I which is maintained at a pressure of about 0.08 inch of mercury absolute pressure. Most of the fatty acids immediately volatilize and cause circulation of undistilled residue contained in the basin ll whereby undistilled residue is projected upwardly against the baffle Hi and deflected so as to form a curtain outward, downward, and away from the vapor outlet. The temperature immediately drops due to volatilization of fatty acids and the fatty acid vapors at a temperature of about 450 F. and at a rate of about 4000 pounds per hour pass through vapor pipe I6 into the series of condensers. By boiling the water in condenser I! under 40 pounds gage pressure, thereby maintaining a condensing temperature of about 287 F., about 3600 pounds of the distilled fatty acids are collected in the first stage of condensation; With the condensing temperature of condenser l8 maintained at approximately 212 F. by boiling the water at atmospheric pressure, the remaining 400 pounds per hour of fatty acid vapors are condensed. Thus about 1000 pounds per hour or 20 per cent of undistilled residue are collected in receiver 3|. This undistilled residue may be charged to a storage tank and after a suitable quantity has been accumulated, it may be rerun through the apparatus under substantially the same conditions used for distilling the original material. This procedure reduces the undistilled residue from approximately 20 per cent to about 12 per cent of the material originally charged to the still.

Example lI.My invention may also be practiced as follows on tallow which has been hydrolyzed to a free fatty acid content of about 97%, a portion of the undistilled residue being recirculated through the heater as above described. The specific data given herein represent those which may be obtained after the still has been in operation sufiiciently long to establish equilibrium.

A mixture of 74.8% of the above referred to hydrolyzed tallow and 25.2% undistilled residue is continuously heated to a temperature of about 515 F. and is continuously introduced into the lower end of the circulating tube which is maintained at an absolute pressure of about 0.16 inch of mercury. Most of the free fatty acids immediately volatilize and cause circulation of undistilled residue contained in the basin as above described. The temperature immediately drops due to volatilization of free fatty acids and the vapors at a temperature of around 400 F. pass through the vapor pipe to suitable condensing equipment. The undistilled residue which consists of about 40% of the total feed to the still and which is at a temperature of about 408 F. is pumped away, about 37.2% being discharged to the undistilled residue receiver and the balance or 62.8% being combined with the incoming new stock and recirculated through the heater. 0n the basis of the new stock fed to the still the undistilled residue amounts to or about 20% and the distlllate amounts m or about If desired the accumulated undistilled residue may of course be rerun as sug-' gested in Example I to recover more free fatty acid therefrom. Thus alowering inthe temperature to which the stock must be heated and/or an increase in distillation pressure may be effected by recirculation as above described.

In following another method of operation, conditions may be controlled so that approximately 30 per cent or more of undistilled residue is discharged to the receiver 3|. If the original stock such as may be obtained by the hydrolysis of a good grade of fat such as tallow, coconut oil, etc., is relatively light in color, the undistilled residue obtained in desired amount by suitable regulation may be used directly in the manufacture of certain soap products such as laundry soap, soap powders, etc., wherein color considerations are of minor importance. The distillate thus obtained from such stocks is extremely light in color, sometimes being as low as 0.3 red (Lovibond color 5 /4" col.) and may be employed in the manufacture of the highest grades of toilet soap. This is an important feature of my process and I believe can only be carried out when the combination of conditions as previously set forth are employed. A batch distillation process yielding 30 per cent, for example, of undistilled residue from the same stocks would not produce products comparable in color, degree of polymerization, etc., because of the length of time the residue is unavoidably subjected to the high temperature of distillation.

Thus by the employment of the following essential features of my process, to wit, dry, low pressure, flash distillation with directionally controlled curtain of residue, it is possible to obtain results which have not heretofore been possible under prior methods of fatty acid distillation.

The raw materials containing fatty acids for use in my process may consist of any fats or fatty oils or materials containing same, such as garbage grease or acidulated soap stock from the refining of fats and oils. In the case of the specific stocks mentioned, any neutral fat in same should ordinarily be first hydrolyzed to fatty acids and glycerin to as high degree as possible and the fatty acids separated before being subjected to distillation. Garbage grease or acidulated soap stock so hydrolyzed will usually contain about ninety per cent or more of free fatty acid calculated as oleic acid. Of course these stocks or lighter colored stocks, such as tallow and palm oil, which sometimes contain twenty-five to fifty per cent free fatty acid, may be subjected to distillation without hydrolysis, the undistilled residue being used directly for any suitable pur pose or being subjected to hydrolysis and subsequent distillation.

This application is a continuation-in-part of application Serial Number 245,440, filed December 13, 1938, and is related to my copending application Serial No. 320,825, filed February 26, 1940.

Having thus described my invention, what I claimv and desire to secure by Letters Patent is:

I. A process of continuously distilling at reduced pressure without the use of an added gaseous medium higher fatty acids from a material containing a substantial amount of higher free fatty acid and thereby separating said material into a component consisting of most of the free fatty acids in substantially pure form and a component consisting of undistilled residue,

comprising continuously passing the material to be subjected to distillation through a heating zone wherein sufificient heat is incorporated in said material to effect substantially instantaneous vaporization of most of the free fatty acids contained therein when subsequently subjected to said reduced pressure continuously introducing the thus heated material into a hot liquid body of said undistilled residue contained within a zone maintained at a pressure not substantially exceeding 0.5 inch of mercury whereupon most of the free fatty acids vaporize substantially instantaneously, employing the vapors thus formed without the aid of an added gaseous medium to project said residue upwardly against a baiiie to form a directionally controlled curtain of said residue, continuously withdrawing the vapors from said zone and condensing same, and continuously withdrawing excess undistilled residue from said zone.

2. A process of continuously distilling at reduced pressure without the use of an added gaseous medium higher fatty acids from a material containing a substantial amount of higher free fatty acid and thereby separating said material into a component consisting of most of the free fatty acids in substantially pure form and a component consisting of undistilled residue, comprising continuously passing the material to be subjected to distillation through a heating zone wherein suflicient heat is incorporated in said material to effect substantially instantaneous vaporization of most of the free fatty acids contained therein when subsequently subjected to said reduced pressure, continuously introducing the thus heated material into a hot liquid body of said undistilled residue contained within a zone maintained at a pressure not exceeding 0.1 inch of mercury whereupon most of the free fatty acids vaporize substantially instantaneously, employing the vapors thus formed without the aid of an added gaseous medium to project said residue upwardly against a bafile toform a directionally controlled curtain of same, continuously withdrawing the vapors from said zone and condensing same, and continuously withdrawing excess undistilled residue from said zone.

3. A process of continuously distilling at reduced pressure without the use of an added gaseous medium higher fatty acids from a material containing a substantial amount of higher free fatty acid and thereby separating said material into a component consisting of most of the free fatty acids in substantially pure form and a component consisting of undistilled residue comprising continuously passing the material to be subjected to distillation through a heating zone wherein suiflcient heat is incorporated in said material to effect substantially instantaneous vaporization of most of the free fatty acids contained therein when subsequently subjected to said reduced pressure and wherein the pressure on the material passing therethrough is progressively reduced, continuously introducing the thus heated material into a hot liquid body of said undistilled residue contained within a zone maintained at a pressure not substantially exceeding 0.5 inch of mercury whereupon most of the free fatty acids vaporize substantially instantaneously, employing the vapors thus formed without the aid of an added gaseous medium to project said residue upwardly" against a baffle, continuously withdrawing the vapors from said zone and condensing same, and continuously withdrawing excess undistilled residue from said zone.

4. A process of continuously distilling at reduced pressure without the use of an added gaseous medium higher fatty acids from a material containing a substantial amount of higher fatty acid and thereby separating said material into a componentconsisting of most of thefree fatty acids in substantially pure form and a component consisting of undistilled residue, comprising continuously passing the'material to be subjected to distillation through a heating zone wherein the said material is heated to a temperature of about 550 to 575 F., continuously introducing the thus heated material into a hot liquid body of said undistilled residue contained within a zone maintained at a pressure of about 0.05 to about 0.1 inch mercury whereupon most of the free fatty acids contained therein vaporize substantially instantaneously, employing the vapors thus formed without the aid of an added gaseous medium to project said residue upwardlyagainst a bafile to form a directionally controlled curtain of said residue, continuously withdrawing the vapors from said zone and condensing same, and continuously'withdrawing excess undistilled res idue from said zone.

5. In a continuous process of low pressure, dry, flash distillation of fatty acids including the step of continuously and rapidly heating a fattyacid-containing material to incorporate therein sumcient heat for vaporization of most of the fatty acids contained therein and the step of condensing the vaporized fatty acids, that step which consists in projecting without the aid of an added gaseous vmedium undistilled residue from the material subjected to distillation intimately admixed with vaporized fatty acids from heated fatty-acid-containing material against a battle in a low pressure distillation zone, the said projecting being effected by the introduction of said heated material into a hot body of said residue in said zone and by the controlled directlonal flow of the vapors formed when the said heated material is subjected to reduced pressure.

6. In a continuous process of low pressure, dry, flash distillation of fatty acids including the step of continuously and rapidly heating a fattyacid-containing material to incorporate therein suflicient heat for vaporization of most of the fatty acids contained therein and the step of condensing the vaporized fatty acids, the steps of maintaining in a low pressure distillation zone a body of hot undistilled residue obtained from material subjected to distillation, introducing said heated fatty-acidcontaining material into said residue, directionally controlling said introduction so as to project said residue without the aid of an added gaseous medium in intimate admixture with fatty acid vapors formed on the introduction of said heated fatty-acid-containing material against a baflle in said zone wherebya curtain of undistilled residue is formed and directed away from the vapor outlet of said zone. '7. In a continuous process of low pressure, dry flash distillation of fatty acids including the step trainment.

of introducing into a suitable low pressure vaporization zone a fatty-acid containing material containing sumcient heat for vaporization of most of the fatty acids, in which zone a vapor portion and an undistilled residue portion are formed from said fatty-acid-containing material, and the steps of removing and condensing the vaporized portion without the aid of an added gaseous medium, that step of employing the vaporized portion to circulate undistilled residue to set up a curtain of same directed away from the vapor outlet of said zone and thereby minimize en- 8. In a continuous process-of low pressure, dry, flash distillation of fatty acids including the step of introducing into a suitable low pressure vaporization zone a. fatty-acid-containing material containing sufllcien't heat for vaporization of most of the fatty acids, in which zone a vapor portion and an undistilled residue portion are formed from said fatty-acidi-containing material, and the steps of removing and condensing the vaporized portion, that step of flashing the heated fatty-acid-containing material into a body of said residue so as to form without the aid of an added gaseous medium a controlled curtain of said residue directed away from the outlet for said vapors.

tained therein when subsequently subjected to said reduced pressure, continuously introducing the thus heated material into a hot liquid body of said undistilled residue contained within a zone maintained at a pressure not substantially exceeding 0.5 inch of mercury whereupon most of the free fatty. acids vaporize substantially instantaneously, employing the vapors thus formed without the aid of an added gaseous medium to continuously project said residue upwardly against a baflle to form a directionally controlled curtain of said residue, continuously withdrawing the vapors from said zone and condensing same, continuously withdrawing excess undistilled residue from said zone, and returning a portion of said excess undistilled residue to the original fatty-acidecontaining material prior to heating.

9. A process of continuously distilling at reprising continuously passing the material to be subjected to distillation through a heating zone wherein suificient heat is incorporated in said material to efiect substantially instantaneous vaporization of most of the free fatty acids con- 10. In a continuous process of-low pressure, dry, flash distillation of fatty acids including the step of continuously and rapidly heating 'a fatty,- acid-containing material to incorporate therein sufllcient heat for vaporization of most of the fatty acids contained therein and the step of condensing the vaporized fatty acids, the steps of maintaining in a low pressure distillation zone a body of hot undistilled residue obtained from heated fatty-acid-containing material into said residue, directionally controlling said introduction so as to project said residue without the aid of an added gaseous medium in intimate admixture with fatty acid vapors formed on the introduction of said heated fatty-acid-containing material against a baflie in said zone whereby a curtain of undistilled residue is formed and directed away from the vapor outlet of said zone, the control of the flow of the fatty-acid-containing material being applied ahead of the heating step. i

- VICTOR MILLS. 

